external/webkit r30707

1 files changed, 781 insertions, 0 deletions

diff --git a/WebCore/loader/TextResourceDecoder.cpp b/WebCore/loader/TextResourceDecoder.cpp
new file mode 100644
index 0000000..ef8a979
--- /dev/null
+++ b/WebCore/loader/TextResourceDecoder.cpp
@@ -0,0 +1,781 @@
+/*
+    Copyright (C) 1999 Lars Knoll (knoll@mpi-hd.mpg.de)
+    Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
+    Copyright (C) 2005, 2006, 2007 Alexey Proskuryakov (ap@nypop.com)
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB.  If not, write to
+    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+    Boston, MA 02110-1301, USA.
+*/
+
+
+#include "config.h"
+#include "TextResourceDecoder.h"
+
+#include "DOMImplementation.h"
+#include "HTMLNames.h"
+#include "TextCodec.h"
+#include <wtf/ASCIICType.h>
+
+using namespace WTF;
+
+namespace WebCore {
+
+using namespace HTMLNames;
+
+// You might think we should put these find functions elsewhere, perhaps with the
+// similar functions that operate on UChar, but arguably only the decoder has
+// a reason to process strings of char rather than UChar.
+
+static int find(const char* subject, size_t subjectLength, const char* target)
+{
+    size_t targetLength = strlen(target);
+    if (targetLength > subjectLength)
+        return -1;
+    for (size_t i = 0; i <= subjectLength - targetLength; ++i) {
+        bool match = true;
+        for (size_t j = 0; j < targetLength; ++j) {
+            if (subject[i + j] != target[j]) {
+                match = false;
+                break;
+            }
+        }
+        if (match)
+            return i;
+    }
+    return -1;
+}
+
+static int findIgnoringCase(const char* subject, size_t subjectLength, const char* target)
+{
+    size_t targetLength = strlen(target);
+    if (targetLength > subjectLength)
+        return -1;
+#ifndef NDEBUG
+    for (size_t i = 0; i < targetLength; ++i)
+        ASSERT(isASCIILower(target[i]));
+#endif
+    for (size_t i = 0; i <= subjectLength - targetLength; ++i) {
+        bool match = true;
+        for (size_t j = 0; j < targetLength; ++j) {
+            if (toASCIILower(subject[i + j]) != target[j]) {
+                match = false;
+                break;
+            }
+        }
+        if (match)
+            return i;
+    }
+    return -1;
+}
+
+static TextEncoding findTextEncoding(const char* encodingName, int length)
+{
+    Vector<char, 64> buffer(length + 1);
+    memcpy(buffer.data(), encodingName, length);
+    buffer[length] = '\0';
+    return buffer.data();
+}
+
+class KanjiCode {
+public:
+    enum Type { ASCII, JIS, EUC, SJIS, UTF16, UTF8 };
+    static enum Type judge(const char* str, int length);
+    static const int ESC = 0x1b;
+    static const unsigned char sjisMap[256];
+    static int ISkanji(int code)
+    {
+        if (code >= 0x100)
+            return 0;
+        return sjisMap[code & 0xff] & 1;
+    }
+    static int ISkana(int code)
+    {
+        if (code >= 0x100)
+            return 0;
+        return sjisMap[code & 0xff] & 2;
+    }
+};
+
+const unsigned char KanjiCode::sjisMap[256] = {
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+    0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0
+};
+
+/*
+ * EUC-JP is
+ *     [0xa1 - 0xfe][0xa1 - 0xfe]
+ *     0x8e[0xa1 - 0xfe](SS2)
+ *     0x8f[0xa1 - 0xfe][0xa1 - 0xfe](SS3)
+ *
+ * Shift_Jis is
+ *     [0x81 - 0x9f, 0xe0 - 0xef(0xfe?)][0x40 - 0x7e, 0x80 - 0xfc]
+ *
+ * Shift_Jis Hankaku Kana is
+ *     [0xa1 - 0xdf]
+ */
+
+/*
+ * KanjiCode::judge() is based on judge_jcode() from jvim
+ *     http://hp.vector.co.jp/authors/VA003457/vim/
+ *
+ * Special Thanks to Kenichi Tsuchida
+ */
+
+enum KanjiCode::Type KanjiCode::judge(const char* str, int size)
+{
+    enum Type code;
+    int i;
+    int bfr = false;            /* Kana Moji */
+    int bfk = 0;                /* EUC Kana */
+    int sjis = 0;
+    int euc = 0;
+
+    const unsigned char* ptr = reinterpret_cast<const unsigned char*>(str);
+
+    code = ASCII;
+
+    i = 0;
+    while (i < size) {
+        if (ptr[i] == ESC && (size - i >= 3)) {
+            if ((ptr[i + 1] == '$' && ptr[i + 2] == 'B')
+            || (ptr[i + 1] == '(' && ptr[i + 2] == 'B')) {
+                code = JIS;
+                goto breakBreak;
+            } else if ((ptr[i + 1] == '$' && ptr[i + 2] == '@')
+                    || (ptr[i + 1] == '(' && ptr[i + 2] == 'J')) {
+                code = JIS;
+                goto breakBreak;
+            } else if (ptr[i + 1] == '(' && ptr[i + 2] == 'I') {
+                code = JIS;
+                i += 3;
+            } else if (ptr[i + 1] == ')' && ptr[i + 2] == 'I') {
+                code = JIS;
+                i += 3;
+            } else {
+                i++;
+            }
+            bfr = false;
+            bfk = 0;
+        } else {
+            if (ptr[i] < 0x20) {
+                bfr = false;
+                bfk = 0;
+                /* ?? check kudokuten ?? && ?? hiragana ?? */
+                if ((i >= 2) && (ptr[i - 2] == 0x81)
+                        && (0x41 <= ptr[i - 1] && ptr[i - 1] <= 0x49)) {
+                    code = SJIS;
+                    sjis += 100;        /* kudokuten */
+                } else if ((i >= 2) && (ptr[i - 2] == 0xa1)
+                        && (0xa2 <= ptr[i - 1] && ptr[i - 1] <= 0xaa)) {
+                    code = EUC;
+                    euc += 100;         /* kudokuten */
+                } else if ((i >= 2) && (ptr[i - 2] == 0x82) && (0xa0 <= ptr[i - 1])) {
+                    sjis += 40;         /* hiragana */
+                } else if ((i >= 2) && (ptr[i - 2] == 0xa4) && (0xa0 <= ptr[i - 1])) {
+                    euc += 40;          /* hiragana */
+                }
+            } else {
+                /* ?? check hiragana or katana ?? */
+                if ((size - i > 1) && (ptr[i] == 0x82) && (0xa0 <= ptr[i + 1])) {
+                    sjis++;     /* hiragana */
+                } else if ((size - i > 1) && (ptr[i] == 0x83)
+                         && (0x40 <= ptr[i + 1] && ptr[i + 1] <= 0x9f)) {
+                    sjis++;     /* katakana */
+                } else if ((size - i > 1) && (ptr[i] == 0xa4) && (0xa0 <= ptr[i + 1])) {
+                    euc++;      /* hiragana */
+                } else if ((size - i > 1) && (ptr[i] == 0xa5) && (0xa0 <= ptr[i + 1])) {
+                    euc++;      /* katakana */
+                }
+                if (bfr) {
+                    if ((i >= 1) && (0x40 <= ptr[i] && ptr[i] <= 0xa0) && ISkanji(ptr[i - 1])) {
+                        code = SJIS;
+                        goto breakBreak;
+                    } else if ((i >= 1) && (0x81 <= ptr[i - 1] && ptr[i - 1] <= 0x9f) && ((0x40 <= ptr[i] && ptr[i] < 0x7e) || (0x7e < ptr[i] && ptr[i] <= 0xfc))) {
+                        code = SJIS;
+                        goto breakBreak;
+                    } else if ((i >= 1) && (0xfd <= ptr[i] && ptr[i] <= 0xfe) && (0xa1 <= ptr[i - 1] && ptr[i - 1] <= 0xfe)) {
+                        code = EUC;
+                        goto breakBreak;
+                    } else if ((i >= 1) && (0xfd <= ptr[i - 1] && ptr[i - 1] <= 0xfe) && (0xa1 <= ptr[i] && ptr[i] <= 0xfe)) {
+                        code = EUC;
+                        goto breakBreak;
+                    } else if ((i >= 1) && (ptr[i] < 0xa0 || 0xdf < ptr[i]) && (0x8e == ptr[i - 1])) {
+                        code = SJIS;
+                        goto breakBreak;
+                    } else if (ptr[i] <= 0x7f) {
+                        code = SJIS;
+                        goto breakBreak;
+                    } else {
+                        if (0xa1 <= ptr[i] && ptr[i] <= 0xa6) {
+                            euc++;      /* sjis hankaku kana kigo */
+                        } else if (0xa1 <= ptr[i] && ptr[i] <= 0xdf) {
+                            ;           /* sjis hankaku kana */
+                        } else if (0xa1 <= ptr[i] && ptr[i] <= 0xfe) {
+                            euc++;
+                        } else if (0x8e == ptr[i]) {
+                            euc++;
+                        } else if (0x20 <= ptr[i] && ptr[i] <= 0x7f) {
+                            sjis++;
+                        }
+                        bfr = false;
+                        bfk = 0;
+                    }
+                } else if (0x8e == ptr[i]) {
+                    if (size - i <= 1) {
+                        ;
+                    } else if (0xa1 <= ptr[i + 1] && ptr[i + 1] <= 0xdf) {
+                        /* EUC KANA or SJIS KANJI */
+                        if (bfk == 1) {
+                            euc += 100;
+                        }
+                        bfk++;
+                        i++;
+                    } else {
+                        /* SJIS only */
+                        code = SJIS;
+                        goto breakBreak;
+                    }
+                } else if (0x81 <= ptr[i] && ptr[i] <= 0x9f) {
+                    /* SJIS only */
+                    code = SJIS;
+                    if ((size - i >= 1)
+                            && ((0x40 <= ptr[i + 1] && ptr[i + 1] <= 0x7e)
+                            || (0x80 <= ptr[i + 1] && ptr[i + 1] <= 0xfc))) {
+                        goto breakBreak;
+                    }
+                } else if (0xfd <= ptr[i] && ptr[i] <= 0xfe) {
+                    /* EUC only */
+                    code = EUC;
+                    if ((size - i >= 1)
+                            && (0xa1 <= ptr[i + 1] && ptr[i + 1] <= 0xfe)) {
+                        goto breakBreak;
+                    }
+                } else if (ptr[i] <= 0x7f) {
+                    ;
+                } else {
+                    bfr = true;
+                    bfk = 0;
+                }
+            }
+            i++;
+        }
+    }
+    if (code == ASCII) {
+        if (sjis > euc) {
+            code = SJIS;
+        } else if (sjis < euc) {
+            code = EUC;
+        }
+    }
+breakBreak:
+    return (code);
+}
+
+TextResourceDecoder::ContentType TextResourceDecoder::determineContentType(const String& mimeType)
+{
+    if (equalIgnoringCase(mimeType, "text/css"))
+        return CSS;
+    if (equalIgnoringCase(mimeType, "text/html"))
+        return HTML;
+    if (DOMImplementation::isXMLMIMEType(mimeType))
+        return XML;
+    return PlainText;
+}
+
+const TextEncoding& TextResourceDecoder::defaultEncoding(ContentType contentType, const TextEncoding& specifiedDefaultEncoding)
+{
+    // Despite 8.5 "Text/xml with Omitted Charset" of RFC 3023, we assume UTF-8 instead of US-ASCII 
+    // for text/xml. This matches Firefox.
+    if (contentType == XML)
+        return UTF8Encoding();
+    if (!specifiedDefaultEncoding.isValid())
+        return Latin1Encoding();
+    return specifiedDefaultEncoding;
+}
+
+TextResourceDecoder::TextResourceDecoder(const String& mimeType, const TextEncoding& specifiedDefaultEncoding)
+    : RefCounted<TextResourceDecoder>(0)
+    , m_contentType(determineContentType(mimeType))
+    , m_decoder(defaultEncoding(m_contentType, specifiedDefaultEncoding))
+    , m_source(DefaultEncoding)
+    , m_checkedForBOM(false)
+    , m_checkedForCSSCharset(false)
+    , m_checkedForHeadCharset(false)
+{
+}
+
+TextResourceDecoder::~TextResourceDecoder()
+{
+}
+
+void TextResourceDecoder::setEncoding(const TextEncoding& encoding, EncodingSource source)
+{
+    // In case the encoding didn't exist, we keep the old one (helps some sites specifying invalid encodings).
+    if (!encoding.isValid())
+        return;
+
+    if (source == EncodingFromMetaTag || source == EncodingFromXMLHeader || source == EncodingFromCSSCharset)        
+        m_decoder.reset(encoding.closest8BitEquivalent());
+    else
+        m_decoder.reset(encoding);
+
+    m_source = source;
+}
+
+// Returns the position of the encoding string.
+static int findXMLEncoding(const char* str, int len, int& encodingLength)
+{
+    int pos = find(str, len, "encoding");
+    if (pos == -1)
+        return -1;
+    pos += 8;
+    
+    // Skip spaces and stray control characters.
+    while (pos < len && str[pos] <= ' ')
+        ++pos;
+
+    // Skip equals sign.
+    if (pos >= len || str[pos] != '=')
+        return -1;
+    ++pos;
+
+    // Skip spaces and stray control characters.
+    while (pos < len && str[pos] <= ' ')
+        ++pos;
+
+    // Skip quotation mark.
+    if (pos >= len)
+        return - 1;
+    char quoteMark = str[pos];
+    if (quoteMark != '"' && quoteMark != '\'')
+        return -1;
+    ++pos;
+
+    // Find the trailing quotation mark.
+    int end = pos;
+    while (end < len && str[end] != quoteMark)
+        ++end;
+    if (end >= len)
+        return -1;
+
+    encodingLength = end - pos;
+    return pos;
+}
+
+// true if there is more to parse
+static inline bool skipWhitespace(const char*& pos, const char* dataEnd)
+{
+    while (pos < dataEnd && (*pos == '\t' || *pos == ' '))
+        ++pos;
+    return pos != dataEnd;
+}
+
+void TextResourceDecoder::checkForBOM(const char* data, size_t len)
+{
+    // Check for UTF-16/32 or UTF-8 BOM mark at the beginning, which is a sure sign of a Unicode encoding.
+
+    if (m_source == UserChosenEncoding) {
+        // FIXME: Maybe a BOM should override even a user-chosen encoding.
+        m_checkedForBOM = true;
+        return;
+    }
+
+    // Check if we have enough data.
+    size_t bufferLength = m_buffer.size();
+    if (bufferLength + len < 4)
+        return;
+
+    m_checkedForBOM = true;
+
+    // Extract the first four bytes.
+    // Handle the case where some of bytes are already in the buffer.
+    // The last byte is always guaranteed to not be in the buffer.
+    const unsigned char* udata = reinterpret_cast<const unsigned char*>(data);
+    unsigned char c1 = bufferLength >= 1 ? m_buffer[0] : *udata++;
+    unsigned char c2 = bufferLength >= 2 ? m_buffer[1] : *udata++;
+    unsigned char c3 = bufferLength >= 3 ? m_buffer[2] : *udata++;
+    ASSERT(bufferLength < 4);
+    unsigned char c4 = *udata;
+
+    // Check for the BOM.
+    if (c1 == 0xFF && c2 == 0xFE) {
+        if (c3 !=0 || c4 != 0)
+            setEncoding(UTF16LittleEndianEncoding(), AutoDetectedEncoding);
+        else 
+            setEncoding(UTF32LittleEndianEncoding(), AutoDetectedEncoding);
+    }
+    else if (c1 == 0xEF && c2 == 0xBB && c3 == 0xBF)
+        setEncoding(UTF8Encoding(), AutoDetectedEncoding);
+    else if (c1 == 0xFE && c2 == 0xFF)
+        setEncoding(UTF16BigEndianEncoding(), AutoDetectedEncoding);
+    else if (c1 == 0 && c2 == 0 && c3 == 0xFE && c4 == 0xFF)
+        setEncoding(UTF32BigEndianEncoding(), AutoDetectedEncoding);
+}
+
+bool TextResourceDecoder::checkForCSSCharset(const char* data, size_t len, bool& movedDataToBuffer)
+{
+    if (m_source != DefaultEncoding) {
+        m_checkedForCSSCharset = true;
+        return true;
+    }
+
+    size_t oldSize = m_buffer.size();
+    m_buffer.grow(oldSize + len);
+    memcpy(m_buffer.data() + oldSize, data, len);
+
+    movedDataToBuffer = true;
+
+    if (m_buffer.size() > 8) { // strlen("@charset") == 8
+        const char* dataStart = m_buffer.data();
+        const char* dataEnd = dataStart + m_buffer.size();
+
+        if (dataStart[0] == '@' && dataStart[1] == 'c' && dataStart[2] == 'h' && dataStart[3] == 'a' && dataStart[4] == 'r' && 
+            dataStart[5] == 's' && dataStart[6] == 'e' && dataStart[7] == 't') {
+    
+            dataStart += 8;
+            const char* pos = dataStart;
+            if (!skipWhitespace(pos, dataEnd))
+                return false;
+
+            if (*pos == '"' || *pos == '\'') {
+                char quotationMark = *pos;
+                ++pos;
+                dataStart = pos;
+            
+                while (pos < dataEnd && *pos != quotationMark)
+                    ++pos;
+                if (pos == dataEnd)
+                    return false;
+
+                int encodingNameLength = pos - dataStart + 1;
+                
+                ++pos;
+                if (!skipWhitespace(pos, dataEnd))
+                    return false;
+
+                if (*pos == ';')
+                    setEncoding(findTextEncoding(dataStart, encodingNameLength), EncodingFromCSSCharset);
+            }
+        }
+        m_checkedForCSSCharset = true;
+        return true;
+    }
+    return false;
+}
+
+// Other browsers allow comments in the head section, so we need to also.
+// It's important not to look for tags inside the comments.
+static inline void skipComment(const char*& ptr, const char* pEnd)
+{
+    const char* p = ptr;
+    // Allow <!-->; other browsers do.
+    if (*p == '>') {
+        p++;
+    } else {
+        while (p != pEnd) {
+            if (*p == '-') {
+                // This is the real end of comment, "-->".
+                if (p[1] == '-' && p[2] == '>') {
+                    p += 3;
+                    break;
+                }
+                // This is the incorrect end of comment that other browsers allow, "--!>".
+                if (p[1] == '-' && p[2] == '!' && p[3] == '>') {
+                    p += 4;
+                    break;
+                }
+            }
+            p++;
+        }
+    }
+    ptr = p;
+}
+
+bool TextResourceDecoder::checkForHeadCharset(const char* data, size_t len, bool& movedDataToBuffer)
+{
+    if (m_source != DefaultEncoding) {
+        m_checkedForHeadCharset = true;
+        return true;
+    }
+
+    // This is not completely efficient, since the function might go
+    // through the HTML head several times.
+
+    size_t oldSize = m_buffer.size();
+    m_buffer.grow(oldSize + len);
+    memcpy(m_buffer.data() + oldSize, data, len);
+
+    movedDataToBuffer = true;
+
+    const char* ptr = m_buffer.data();
+    const char* pEnd = ptr + m_buffer.size();
+
+    // Is there enough data available to check for XML declaration?
+    if (m_buffer.size() < 8)
+        return false;
+
+    // Handle XML declaration, which can have encoding in it. This encoding is honored even for HTML documents.
+    // It is an error for an XML declaration not to be at the start of an XML document, and it is ignored in HTML documents in such case.
+    if (ptr[0] == '<' && ptr[1] == '?' && ptr[2] == 'x' && ptr[3] == 'm' && ptr[4] == 'l') {
+        const char* xmlDeclarationEnd = ptr;
+        while (xmlDeclarationEnd != pEnd && *xmlDeclarationEnd != '>')
+            ++xmlDeclarationEnd;
+        if (xmlDeclarationEnd == pEnd)
+            return false;
+        // No need for +1, because we have an extra "?" to lose at the end of XML declaration.
+        int len;
+        int pos = findXMLEncoding(ptr, xmlDeclarationEnd - ptr, len);
+        if (pos != -1)
+            setEncoding(findTextEncoding(ptr + pos, len), EncodingFromXMLHeader);
+        // continue looking for a charset - it may be specified in an HTTP-Equiv meta
+    } else if (ptr[0] == '<' && ptr[1] == 0 && ptr[2] == '?' && ptr[3] == 0 && ptr[4] == 'x' && ptr[5] == 0) {
+        setEncoding(UTF16LittleEndianEncoding(), AutoDetectedEncoding);
+        return true;
+    } else if (ptr[0] == 0 && ptr[1] == '<' && ptr[2] == 0 && ptr[3] == '?' && ptr[4] == 0 && ptr[5] == 'x') {
+        setEncoding(UTF16BigEndianEncoding(), AutoDetectedEncoding);
+        return true;
+    } else if (ptr[0] == '<' && ptr[1] == 0 && ptr[2] == 0 && ptr[3] == 0 && ptr[4] == '?' && ptr[5] == 0 && ptr[6] == 0 && ptr[7] == 0) {
+        setEncoding(UTF32LittleEndianEncoding(), AutoDetectedEncoding);
+        return true;
+    } else if (ptr[0] == 0 && ptr[1] == 0 && ptr[2] == 0 && ptr[3] == '<' && ptr[4] == 0 && ptr[5] == 0 && ptr[6] == 0 && ptr[7] == '?') {
+        setEncoding(UTF32BigEndianEncoding(), AutoDetectedEncoding);
+        return true;
+    }
+
+    // we still don't have an encoding, and are in the head
+    // the following tags are allowed in <head>:
+    // SCRIPT|STYLE|META|LINK|OBJECT|TITLE|BASE
+    
+    // We stop scanning when a tag that is not permitted in <head>
+    // is seen, rather when </head> is seen, because that more closely
+    // matches behavior in other browsers; more details in
+    // <http://bugs.webkit.org/show_bug.cgi?id=3590>.
+    
+    // Additionally, we ignore things that looks like tags in <title>, <script> and <noscript>; see
+    // <http://bugs.webkit.org/show_bug.cgi?id=4560>, <http://bugs.webkit.org/show_bug.cgi?id=12165>
+    // and <http://bugs.webkit.org/show_bug.cgi?id=12389>.
+
+    // Since many sites have charset declarations after <body> or other tags that are disallowed in <head>,
+    // we don't bail out until we've checked at least 512 bytes of input.
+
+    AtomicStringImpl* enclosingTagName = 0;
+
+    while (ptr + 3 < pEnd) { // +3 guarantees that "<!--" fits in the buffer - and certainly we aren't going to lose any "charset" that way.
+        if (*ptr == '<') {
+            bool end = false;
+            ptr++;
+
+            // Handle comments.
+            if (ptr[0] == '!' && ptr[1] == '-' && ptr[2] == '-') {
+                ptr += 3;
+                skipComment(ptr, pEnd);
+                continue;
+            }
+
+            // the HTTP-EQUIV meta has no effect on XHTML
+            if (m_contentType == XML)
+                return true;
+
+            if (*ptr == '/') {
+                ++ptr;
+                end = true;
+            }
+
+            // Grab the tag name, but mostly ignore namespaces.
+            bool sawNamespace = false;
+            char tagBuffer[20];
+            int len = 0;
+            while (len < 19) {
+                if (ptr == pEnd)
+                    return false;
+                char c = *ptr;
+                if (c == ':') {
+                    len = 0;
+                    sawNamespace = true;
+                    ptr++;
+                    continue;
+                }
+                if (c >= 'a' && c <= 'z' || c >= '0' && c <= '9')
+                    ;
+                else if (c >= 'A' && c <= 'Z')
+                    c += 'a' - 'A';
+                else
+                    break;
+                tagBuffer[len++] = c;
+                ptr++;
+            }
+            tagBuffer[len] = 0;
+            AtomicString tag(tagBuffer);
+            
+            if (enclosingTagName) {
+                if (end && tag.impl() == enclosingTagName)
+                    enclosingTagName = 0;
+            } else {
+                if (tag == titleTag)
+                    enclosingTagName = titleTag.localName().impl();
+                else if (tag == scriptTag)
+                    enclosingTagName = scriptTag.localName().impl();
+                else if (tag == noscriptTag)
+                    enclosingTagName = noscriptTag.localName().impl();
+            }
+            
+            // Find where the opening tag ends.
+            const char* tagContentStart = ptr;
+            if (!end) {
+                while (ptr != pEnd && *ptr != '>') {
+                    if (*ptr == '\'' || *ptr == '"') {
+                        char quoteMark = *ptr;
+                        ++ptr;
+                        while (ptr != pEnd && *ptr != quoteMark)
+                            ++ptr;
+                        if (ptr == pEnd)
+                            return false;
+                    }
+                    ++ptr;
+                }
+                if (ptr == pEnd)
+                    return false;
+                ++ptr;
+            }
+            
+            if (!end && tag == metaTag && !sawNamespace) {
+                const char* str = tagContentStart;
+                int length = ptr - tagContentStart;
+                int pos = 0;
+                while (pos < length) {
+                    int charsetPos = findIgnoringCase(str + pos, length, "charset");
+                    if (charsetPos == -1)
+                        break;
+                    pos += charsetPos + 7;
+                    // skip whitespace
+                    while (pos < length && str[pos] <= ' ')
+                        pos++;
+                    if (pos == length)
+                        break;
+                    if (str[pos++] != '=')
+                        continue;
+                    while (pos < length &&
+                            (str[pos] <= ' ') || str[pos] == '=' || str[pos] == '"' || str[pos] == '\'')
+                        pos++;
+
+                    // end ?
+                    if (pos == length)
+                        break;
+                    int end = pos;
+                    while (end < length &&
+                           str[end] != ' ' && str[end] != '"' && str[end] != '\'' &&
+                           str[end] != ';' && str[end] != '>')
+                        end++;
+                    setEncoding(findTextEncoding(str + pos, end - pos), EncodingFromMetaTag);
+                    if (m_source == EncodingFromMetaTag)
+                        return true;
+
+                    if (end >= length || str[end] == '/' || str[end] == '>')
+                        break;
+
+                    pos = end + 1;
+                }
+            } else if (ptr - m_buffer.data() >= 512 && tag != scriptTag && tag != noscriptTag && tag != styleTag &&
+                       tag != linkTag && tag != metaTag && tag != objectTag &&
+                       tag != titleTag && tag != baseTag && 
+                       (end || tag != htmlTag) && !enclosingTagName &&
+                       (tag != headTag) && isASCIIAlpha(tagBuffer[0])) {
+                m_checkedForHeadCharset = true;
+                return true;
+            }
+        }
+        else
+            ptr++;
+    }
+    return false;
+}
+
+void TextResourceDecoder::detectJapaneseEncoding(const char* data, size_t len)
+{
+    switch (KanjiCode::judge(data, len)) {
+        case KanjiCode::JIS:
+            setEncoding("ISO-2022-JP", AutoDetectedEncoding);
+            break;
+        case KanjiCode::EUC:
+            setEncoding("EUC-JP", AutoDetectedEncoding);
+            break;
+        case KanjiCode::SJIS:
+            setEncoding("Shift_JIS", AutoDetectedEncoding);
+            break;
+        case KanjiCode::ASCII:
+        case KanjiCode::UTF16:
+        case KanjiCode::UTF8:
+            break;
+    }
+}
+
+String TextResourceDecoder::decode(const char* data, size_t len)
+{
+    if (!m_checkedForBOM)
+        checkForBOM(data, len);
+
+    bool movedDataToBuffer = false;
+
+    if (m_contentType == CSS && !m_checkedForCSSCharset)
+        if (!checkForCSSCharset(data, len, movedDataToBuffer))
+            return "";
+
+    if ((m_contentType == HTML || m_contentType == XML) && !m_checkedForHeadCharset) // HTML and XML
+        if (!checkForHeadCharset(data, len, movedDataToBuffer))
+            return "";
+
+    // Do the auto-detect if our default encoding is one of the Japanese ones.
+    // FIXME: It seems wrong to change our encoding downstream after we have already done some decoding.
+    if (m_source != UserChosenEncoding && m_source != AutoDetectedEncoding && encoding().isJapanese())
+        detectJapaneseEncoding(data, len);
+
+    ASSERT(encoding().isValid());
+
+    if (m_buffer.isEmpty())
+        return m_decoder.decode(data, len);
+
+    if (!movedDataToBuffer) {
+        size_t oldSize = m_buffer.size();
+        m_buffer.grow(oldSize + len);
+        memcpy(m_buffer.data() + oldSize, data, len);
+    }
+
+    String result = m_decoder.decode(m_buffer.data(), m_buffer.size());
+    m_buffer.clear();
+    return result;
+}
+
+String TextResourceDecoder::flush()
+{
+    String result = m_decoder.decode(m_buffer.data(), m_buffer.size(), true);
+    m_buffer.clear();
+    return result;
+}
+
+}